The history of windows

Windows are something that many of us take for granted. But, yet, what we often fail to realise is that windows are not historically universal. They have evolved throughout history, with their style and manufacturing methods going through radical changes. There are also many people across the world today who do not have windows in their homes. To put things into perspective, it’s important to examine the evolution of windows in their millennia-long history.

In its simplest form, a window is a hole in a wall designed to let light in, or depending on the period, to provide protection and a place from which to defend a building. They weren’t particularly weatherproof or secure, as you can imagine. So naturally, a solution was needed whereby light could be allowed in, but heat could be retained and unwanted guests could be kept out. That’s why the history of windows is closely intertwined with the history of glassmaking.

The earliest forms of window originated in the Bronze and Iron Ages in the form of scraped and stretched animal hides. These rudimentary ‘windows’ were dipped in oil to give them waterproof and translucent qualities, and while they were hardly advanced, they provided some major advantages over simply having a hole in the wall. Wooden shutters would be placed over them to provide added protection. The development of windows was slow for many centuries to come.

These developments rapidly accelerated with the invention of glass. Glass provided a basic cover for windows that allowed light in and kept the elements out. Historians believe glass was first used for windows at the end of the first century AD, when the Romans discovered that adding manganese oxide to hides made a clear glass-style substance. These early ‘glass’ windows would be unrecognisable to us today – for a start, the optics were much poorer. Glass windows were also only really available to the rich – they were considered a mark of wealth and status, which is why archaeologists have only been able to find them on the most significant buildings in old historical settlements.

With the eleventh century emerged two new glass making techniques, and for the first time humans had something resembling modern window panes. The techiques involved blowing a ball of molten glass into a bubble. If you’ve ever seen someone make glass by hand, you’ll have a good idea of what this might look like. The bubble was then either pierced and spun into a disc, or swung to form a cylinder. The products were sliced and laid out flat. The panes were then cut from the select sections of that plate – usually the parts with the optimum thickness and transparency.

It was towards the end of the seventeenth century that the French developed a method for producing larger plates of glass with a much higher clarity. Some of these windows can still be seen in France today, particularly in older buildings and cathedrals. This was achieved by pouring the molten glass onto a specially designed table. It was then rolled flat and the surfaces were glazed with a fine abrasive powder. However, this method was yet to overcome the problems humans had faced with windows since the Bronze Age – they were still only accessible to a rich minority! Although this process developed greatly in the nineteenth century, it would not be until the emergence of new mass production techniques that this would fundamentally change.

It was in Belgium during the first World War that glassmaking methods finally became more advanced. Manufacturers would draw ribbons of molten glass from tanks. These ribbons were drawn through rollers to achieve a consistent thickness and a smooth, high quality finish. A few decades later, during the 1950s, the British pioneered the ‘float process’. In this technique, the molten glass is poured across a surface bath of molten tin. The effect of this is that the glass spreads and flattens before being drawn off in a continuous ribbon. This technique produces mass quantities of large and high quality glass and is still mainly used to produce glass for our windows today.

Although there have been many changes to window glass throughout the centuries, all of them have built on the same principles developed by our ancestors long ago. Windows are fundamental to our idea of architecture and interior space, and by looking at their history, we can seek to understand the parallels between ancient history and the structures around us today.